Fuse construction



June 26, 1945. H; A. LEWIS 2,379,013

FUSE CONSTRUCTION Filed Feb. 2'7, 1942 k )IWENTOR HALEW/S w a it/g3 v Ix ATTORNEY Patented June 26, 1945 2,379,013 FUSE CONSTRUCTION Herbert A. Lewis, Port Washington, N. Y., assignor to Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a. corporation of New York Application February 27, 1942, Serial No. 432,675

8 Claims.

This invention relates to electric circuit interrupters generally used in telephone exchanges and particularly to alarm fuses for guarding the apparatus against abnormal currents.

In telephone exchanges it is the practice to assemble alarm type fuses closely together in an upright position upon slate panels, one terminal of the fuse being connected with the common battery bus-bar and the other terminal thereof being connected with the particular wire of an electric circuit or group of circuits. Each slate panel comprises a plurality of fuses and has mounted thereon a common battery bus-bar and common alarm bar. The fuses are of the fiat type, being known in telephone practice as the grasshopper fuse, and when blown this fact is space and cost over the very desirous.

An object of this invention is, therefore, to provide a more economical alarm fuse and tenpresent type of fuse is duces a readily Other objects audible alarng, and at the same time providing a visual target 'to facilitate its replacement. The

fuse consists of an insulating tube slotted for the ready placement therein of a fuse wire which is terminated at each end in a slotted metallic detail. The fuse holder provides springs for mounting a plurality of fuses thereon at close intervals whereby peripheral grooves of the end details are securely engaged by the springs thereof while at the same time easily removable therefrom. A plurality of fuse holders may be mounted upon a panel in tandem or individually, as required.

This invention, accordingly, is disclosed in the embodiment thereof shown in the accompanying drawing, and it comprises the features of construction. combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the application of which will be indicated in the appended cla For a more complete understanding of the nature and scope of this invention, reference may be had to the following detailed description taken in connection with the accompanying drawing, in which:

Fig. 1 illustrates a, perspective view of a pair of fully equipped fuse holders assembled in tandem upon a mounting panel;

Fig. 2 illustrates a top plan view of the right fuse holder of Fig. 1 with portions of the fuse retaining springs and bus-bar extremities exposed;

.Fig. 3 illustrates a detailed cross-sectional view of the holder assembly taken along line 3-3 of Fi 2;

Fig. 4 illustrates a detailed cross section of a view taken along linell of Fig. 2;

Fig. 5 illustrates a longitudinal section of the fuse; and

Fig. 6 illustrates a cross-sectional view of the fuse taken along line 6-6 of Fig. 5.

Referring now to Fig. l, a mounting panel Ill of the usual type supports a plurality of fuse holders ll, each of which has a capacity of ten fuses l2, so that for a single mounting panel of 2'3 inch length four fuse holders l I or a total of forty fuses l2 may be accommodated thereon in a vertical space of 1% inches. The invention, however, is not to be limited to this quantity of fuses as the number of fuses accommodated will be dependent upon various factors including the length of panel l0 and the installation requirements.

The fuse holder i i (Fig. 3) comprises a receptacle of rectangular shape having a top, bottom. and back with open sides and face. The top assembly includes a pairof insulating plates i3, ill, the upper plate It cooperating with the lower plate l4 to embracingly clamp individual springs of contact material, such as nickel silver. In order to prevent sliding movement of spring l5, longitudinal slots I! (Fig. 2), one for each spring i6, and a lateral groove l8 are provided in the upper side of plate I4 and a projection i9, punched from the main portion of spring I6, is also provided to entersaid groove IB. Spring it has formed at one end a terminal 2|) for connection to wire 2| of the circuit being protected and at the other end a bifurcation 22 with a longitudinal slot for tensionally supporting the upper part of fuse l2. to plate I4 in any suitable manner such as by screws 23 threadedly engaged into plate M.

The bottom assembly comprises an insulating plate 24, similar to plate l3 of the top assembly, and an L-shaped metallic alarm bar 25 extending along the length thereof and fastened thereto in any suitable manner. such as by screws 26 engaging threaded apertures of bar 25. The alarm bar 25 is common to all fuses assembled on mounting ll and is provided with an overlapping means, such as a raised extension 21 (Figs. 1 and 2) at the right end and a tongue 28 at the left end thereof, the extension 21 of one mounting H and tongue 23 of a contiguous mounting l I being connected together by soldering or any other suitable method. Thus a continuous alarm bar is provided for all fuses mounted on panel 10. At one end of continuous bar 25, preferably at terminal 21, connection is made to an alarm circuit wire (not shown).

Separating the bottom from the top assembly is an insulating bar 28, which is attached thereto by the usual bolt and nut combination 3| and which is disposed from the rear edges of the top and bottom plates l3, so as to form a recess therein, to effect engagement by the holder assembly ll of three faces of the mounting panel Iii. Further engagement of panel "I is obtained by screws 32 inserted into threaded apertures of bar 29, thereby producing;

a well supported structure. Screws 32 also socure to panel I! a continuous terminal strip 33 for connection to ground wires 34 of the circuits being protected.

To the front side of bar mon bus-bar 35, of suitable conducting material such as copper, by means of screws 36 threadedly engaging bar 29. Clamped between bus-bar '35 and a clamping bar 31. also by screws 35, is a continuous spring 38 of a combined retractile and contacting material. such as nickel silver. having individual fingers integral thereto. As shown in Fig. 3, the angle formed by retractile finger 39 with spring 38 in the released state is greater than 90 degrees so that when fuse I2 is in position, finger 35 is under tension. Rupture of fuse l2 releases this tension whereupon bar 25 is immediately contacted by finger 39 to close the usual alarm circuit. As in the stationary contact spring IS, the retractile fingers 39 are provided with bifurcations 4! at the extremities thereof with slots 42 extending inwardly to facilitate. installation or replacement of fuse l2. It is to be noted that the diameter of bottom bifurcation 4| is larger than that of the upper bifurcation 22. The reason for this will be apparent hereinafter.

In order to insure a continuous battery connection for all fuse mountings H mounted on panel "I, each bus-bar 35 is joined to its neigh- Upper plate 13 may be fastened l4 and 24, respectively,

25 is attached a com-:

boring car. As shown in Fig. 2, bus-bar 35 has at its left extremity an extension 43, which may be approximately one-hall the thickness of busbar 35 proper with a cut-out in the front thereof and which is provided with a threaded aperture for engaging a screw 44, that. may be staked at its threaded end to prevent accidental removal. At the right extremity of bus-bar 35 another extension 45 is provided with the cut-out at its back portion, instead. so as to mesh with its contiguous bus-bar extension 43. A slot, as shown in Fig. 4, is provided in extension 46, as well as in clamping bar 31, for facilitating the assembly of contiguous fuse mountings II. The juncture of one bus-bar 35 with an adjoining one is shown at the left of Fig. 2 wherein the dot-dash lines represent the bus-bar extremity 46 and clamping bar 31 of the left mounting H secured to the busbar extremity 43 by screw 44 of the right, fuse mounting ll. Screw 44 (Fig. 1) also secures a battery lead (not shown) to the bus-bar extremity 43 of the left fuse mounting ll assembled to panel 10.

Fuse l2, as shown in Fig. 5, comprises four items, two metallic terminal details 41, 48, an insulating tube 49 having a longitudinal slot 5i therein. and a fuse wire 52 connected to terminal details 41, 48, by soldering or by any other suitable means. Terminals 41 and 48 may be silver plated to insure low contact resistance. Both terminals 41 and 4B, which can be readily and economically machined, have circumferential grooves 53 and 54, respectively, groove 53 being of smaller diameter than groove 54 in order to ina.) sure proper installation of the fuse l2 upon correspondingly slotted Terminals springs" and 4! of mount- 41 and 48 also have longi-- tudinal slots 55, which when aligned with slot 5| of tube 49, simplifies installation or replacement of a fuse wire 52. A shoulder 51 on terminal 41 is detachably coupled to one end of tube 49 while terminal 48 is secured to the other end thereof in any suitable manner as by a threaded arrangement. so that upon rupture of a fuse wire 52 tube 49, being attached to terminal 48,,acts as a target. To facilitate determination of fuse capacities tubes 48 of various colors may be employed as, for example, a black tube may be used for a l -ampere fuse, a red tube may be used for a 2-ampere fuse, etc.

A fuse I2 is assembled upon mounting Ii by forcing the peripheral groove I54 into embracing engagement with slot 4!, which holds terminal 48 securely in place by the detent action of the sides thereof, raising the fuse l2 and engaged finger 39 until groove 53 is in alignment with slot 22, and then forcing groove 53 into similar engagement with slot 22. Upon rupture of a fuse l2 insulating tube 49 confines the disturbance so that adjacent fuses l2 are not aflected; at the same time since tube 45 follows the movement of spring 39 the free end thereof is carried alon the line of the arc lengthening its path and tending to extinguish it. Spring 35- contacts alarm bar 25 and initiates an alarm (not shown) to summon a maintenance man who readily per.-

ceives the blown fuse because of the off-nornml position of tube 49. A new fuse i2 is installed in the place of the blown one and the maintenance man may then remove portions of fuse wire 52 from both terminals 41 and 48 and install a new fuse wire therein in a manner already do.- scribed.

While the features of this invention have been disclosed with reference to a specific embodiment only, it is, of course, understood that various modifications may be made in the details of construction and that the features thereof may be applied to many other and widely varied fields without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. In combination with an electrical fuse holder having interspaced springs, a fuse comprising a plurality of spaced terminals having longitudinal slots, an insulating tube interposed between said terminals, said terminals being slidably engageable with said springs, and a fusible conductor holding said terminals in spaced relationship, said fusible conductor disposed within the tube and within the longitudinal slots for facilitating replacement of said fusible conductor upon rupture thereof.

2. In combination with an electrical fuse holder having interspaced contact springs, a fuse comprising a plurality of spaced, relatively separable terminal members having longitudinal slots, each of said members having a circumferential groove for engagement with said springs, an insulating tube interposed between said members, and a fus wire holding said members in spaced relationship. said wire disposed within the tube and within the slots of said members.

3. In combination with an electrical fuse holder having interspaced springs one of which is tensioned, a fuse comprising a plurality of spaced, relatively separable terminal members, an insulating element interposed between and secured to one of said members, said element having a slot extending longitudinally therein, each of said members having a peripheral recess for slidable engagement with said springs and having a slot for alignment with said element slot, and a fuse wire disposed within said element and within the slots of said members for holding said members in spaced relationship, said wire being soldered to said members.

4. In a circuit interrupter, in combination, an electrical fuse holder having a lower and an upper slotted contact spring, a fuse comprising an insulating element having a longitudinal slot, a first terminal member having a longitudinal slot. said member fixedly secured to one end of said element and havin said slot aligned with said element slot, a second terminal member having a longitudinal slot, said second member detachably coupled to the other end of said element, said first member having a peripheral groove for slidable engagement with the lower contact spring, said second member having a peripheral groove for slidable engagement with the upper contact spring, and a fuse conductor disposed within the element and within the member slots for holding the terminal members in spaced relationship, said element and member slots facilitating installation and replacement of the conductor upon rupture thereof.

5. In a circuit interrupter, in combination, a pair of interspaced line terminals having longitudinal slots. an insulating tubular arcing chamber detachably coupled to one of said terminals and fixedly secured to the other one of said terminals, a fuse wire for interconnecting said terminals, said fuse wire disposed within said arcing chamber and said slots placed in alignment, biasing means for extinguishing an are upon rupture of the fuse wire whereby the terminals are separated and the arcing chamber is drawn along the line of the arc, and means for arresting movement of said arcing chamber, said arcing chamber providing a target for said ruptured fuse.

6. In a circuit interrupter, in combination, a fuse comprising a tubular housing of insulating material having line terminals at the ends thereof, said housing and terminals having longitudinal slots therein, a fuse wire extending from one to the other of said terminals and within said slots, said terminals having circumferential grooves thereon, a holder for a plurality of said fuses comprising means for supporting a plurality of pairs of interspaced springs, said springs being arranged in an upper and a lower row and having bifurcated apertures at the extremities thereof for engaging said grooves, a battery bus bar electrically connected with the springs of the lower row, a common bar associated with said lower contact springs for contactin same upon rupture of any one of said fuses, and means for supporting said holder.

7. Circuit interrupting means comprising, in combination, fuse elements, a holder for a plurality of said fuse elements, and a panel for supporting a plurality of said holders in tandem, each of said fuse elements comprising a tubular housing of insulating material having terminals at the ends thereof, said housing and terminals having longitudinally aligned slots therein, a fuse wire disposed within said slots for interconnecting said terminals, each of said terminals having circumferential grooves for facilitating the disposition thereof on said holder, said holder comprising a plurality of cooperatin stationary and pretensioned springs for engaging the grooves of said fuse elements whereby said fuse elements are tensionally mounted, a battery bus-bar connected to said pretensioned springs, a right and a left extension on said bus bar, means on said left extension for joining the right extension of one of said tandem holder bus-bars thereto, a common bar associated with said pretensioned springs, a right and a left extension on said common bar for joining a plurality of said common bars disposed in tandem, means on said holder for embracingly engaging said panel comprising an oblong metallic member, a continuous strip of terminals individual to each of said holders secured to said panel, and means for interconnecting said common bars.

8. A renewable fuse consisting only of an insulating tube having a longitudinal slot, an end member adaptable for fixed engagement with one end of said tube, a second end member adaptable for abutting engagement with the other end of said tube, each of said end members having a longitudinal slot, and a fuse link disposed in the longitudinal slots in said end member and having its opposite ends joined by adherence to said end members, said fuse link being substantially enclosed within said insulating tube and capable of moving freely in and out of the slots in said tube and end members to enable its ready replacement.

HERBERT A. LEWIS. 

